Method of producing an electrodecarrying silicon semiconductor device



for example, as antimony-sulphide (Sb2S3).

No Drawing. ,APPlicatiom c tober 2'4, 19,58

l,Serial .151047625295 f Claims priority, application ,Germany vNoremher 8, 1957 t tot. .14a-tts Qur :invent-.ion relates to a :rnethnd of producing :a

semiconductor device of silicon' in vulrich. .Que .er electrodes are formed by alloying gold with yan `adrrrlxture nite States Patent of 0.2 to 15%, preferably trennt y1%, antimorty intothe surface of a. monocrvstalh e silicnn fb. Y.' Such fa lmethod .is ldisclosed and Lclairnged in .the --coneuding apyulieation :Serial No :QSI/6.3.1, .etledtMttyV :7, 19.5.7, new tRatent No. 2,898,528. and lassigned/to :the assignee of the present invention. 1

Electric ,semiconductor devices O f the type here s911- serned Amay be designed, afor example, ras rrectiters, -zpower :transistors aphotodiodes or the 'like ...elect devices, :in which one .or more antimony.-containing gold .eleutrodes depending upon the .tuseilof :the device, @refused :and .Y

alloyed .tqsether with .senticchdusr' .argner- The electrodes of such devices 'have been observed to possess faulty alloying spots, particularly i-f the Yantimony-containing vfoil `of .gold used for producing thefslectrmles :was very thin; isthe aaseffqrfte ample, inthe-:mauriffectureoftrausirs.- Ilse-Vorraum@ Of .Suchalloying faults in p-n junction devices p oduced by the abovementioned alloying method has the detrimental result of reducing the inverse voltage to which the p-n junction can be subjected, or the device may completely lose. the desired blocking ability. It has been proposed to mini mize the occurrence of such faulty alloying spots by using, for the alloying process, a gold-antimony alloy with a trace content of arsenic.

It is an object vof our invention to provide a more reliable method of avoiding the formation of faulty alloying spots.

To this end and in accordance with our invention, we produce the electrode or electrodes on the monocrystalline body of silicon by alloying into the surface zone of this body a gold-antimony alloy which contains traces j of sulphur.

in a preliminary or lirst melting process together withV the highly pure antimony. The sulphur may be added to the melt of antimony in pure or in compound form,

The antimony thus provided with a content of sulphur or antimony-sulphide is then admixed to the gold by means of a second melting process and, if desired, by additional melting processes. During the subsequent melting processes the proportion of gold can be increased in steps. In the nal stage the proportionate amounts should be preferably 99% Au and 1% Sb/S.

According to a modified method of the invention, the sulphur is added in pure or compound form, for example as lantmony-sulphide, to a quantity of gold in a first '.,Sgtiri'irlerires lilith A-whitt ,the .Silicon discs faced .0h

ice

2 rheltins presets. The .sold .chastity this tirs-t amar .um be hishlypure r,crit may already .certain auf' yk 'The sulphur or sulphur compound is directly adnnxed :to themelt ofsqli- This Air done bvirst adding the ,Sulphur .er sulphur compound t9 a portion ofthe total ,sold dilatitity, 'and by thereafter performing im@ .9i 1159i@ idilitional melting processes 4by .means of which the ultimate compositqh is A,cdby admitting the ahtlhitlily .tutti stepwise increasing .the'proportion off gold. for eiiample up@ ,the abovefmentioned 'optimum proportion Ot .99'1- Ihe .sulphur-containing ,sOlil-ahtimhy alley vih. .sl in this manriercarrthen be .rolled down .to afoilfhaug a thickness .Qf 9-05 0r less .Inform ,of @11th .a fll the elettwsle metal .can .he .Ghvthhtly :llhdlstl all# ,used :for forming an .electrode @r1 the @tutti .the-manner hientipiiedabsrs- The shlphurecghtaihihg gold-antwort' .alloy :he additionally presided with trace sortent ,of artritis lh accorda with-.the 1s osare ,in the copehfdins ,applittiorrSer 711,1;.96Mi1etl lahtiary 2,9, 19,5.` ,Sith an addititzh .of artritis; rslatllhg tto the rerrehtags by wieht nf the kgoldau,tirtwriv allait. preferably-litri hstwssh lbs ...eliectedin ,a manner described .above with .reference `.to ...the sulphur,-

The -alloyihsnwtst proper sat1 be rrrtqrrnssl, i9! example, ith .the aid Off rssillehtshd adjustable" l sides .with the rahorredertribed @irritatie fails desired? weird Eby .carrier 'Plates his climat-S1 pressure e `ple-offs vlh f. 1.8 um subirse@ .o .heating at approximately 1.0.9 toOO C.;f.0.rafhwshihitt 'ehothe'rihthntl vitoriatins the elertrhslesthy alla iigth istil tgsethsr hrhr-he similar period of time, preferably while applying moderate pressure up to about 1 kg./cm.2 or less, this latter method being more fully disclosed in the copending application Serial No. 637,029, tiled January 29, 1957. In this manner, highly-doped n-type conducting zones can be produced in the silicon dics. Between such a. zone andthe adjacent zone `formed by silicon which remained unaffected by the alloying treatment, there exists a p-n junction if the silicon, prior to the alloying process, had p-type conductives, such a p-n junction having the effect of making the device asymmetrically conducltive.

The above-mentioned melting processes for doping the igold with the above-mentioned additional substances, as well as the above-described alloy-fusion process and any subsequent melting processes as mayY be needed for fastening current supply conductors to the electrodes, are preferably performed in an inert atmosphere, particularly if the process requires a temperature above 500 C. Gases suitable as inert atmospheres are, for example,

argon, nitrogen, carbon monoxide. An addition of borax is to be avoided.

It will be obvious to those skilled in the art, upon a study of this disclosure, that our invention permits of various modifications and alterations with respect to the individual components and method steps disclosed, and hence can be embodied in equipment other 4than as particularly described herein, without departing from the essential features of the invention and within the spirit and scope of the claims annexed hereto.

We claim:

1. A method for producing an electrode-carrying'semi.- conductor device in which the semiconductor is composed of silicon, comprising forming at least one electron of foil thickness on a silicon monocrystal by alloying into said silicon monocrystal a quantity of gold containing from-0.2% to 5% antimony and a trace content of sulphur to form vajunction zone larger than l mm.2 inarea,

Is aril electrode having an area equal to that of said junc- 'tion zone, whereby faulty alloying spots in Vsaid junction zone' are minimized. Y

2. A method according to claim 1, said trace content 3.` A method for producing an electrode-carrying semiconductor device in which the semiconductor is composed of silicon comprising forming at least one electrode of foil thickness on a silicon monocrystal by alloying into said silicon monocrystal a quantity of gold containing fr0m0.2% to 5% antimony and between 104% Ling 104% sulphur to (form a junction zone between said electrode and said monocrystal, said electrode hav- 4ingan-'area equal to that of said junction zone, said sulphur-containing gold-antimony alloy being prepared by admixing a material selected from the group consisting ofsulphur, Sb2S3 and Sb2S5, admixing said selected material with highly pure antimony in a first melting step, and admixing the product of said rst melting step to gold of high purityA in at least one subsequent melting step, whereby faulty alloying spots in said junction zone are minimized.

4. A method for producing an electrode-carrying semiconductor device in which the semiconductor is composed of silicon, comprising admixing, in a rst melting step, a

Yquantity of sulphur contained in a material selected of sulphur being between l04% and l01% by Weight i' 'of the total gold-antimony alloy.

equal to that of said junction zone, whereby faulty alloying spots in said junction zone are minimized.

5. A method for producing an electrode-carrying semiconductor device in which the semiconductor is composed of silicon, comprising forming at least one electrode of foil thickness on a silicon monocrystal by alloying into saidsilicon monocrystal a quantity of gold alloy containing from 0.2% to 5% antimony by weight, from l0*4% to itl-1% sulphur by weight, and containing a trace content of arsenic to form a junction zone between said electrode and said monocrystal, said electroderhaving an area equal ot that of said junction zone, whereby faulty alloying spots in said junction zone are minimized.

6. A method for producing an electrode-carrying'semiconductor device in which the semiconductor is composed of silicon, comprising forming at least one electrode of foil thickness on a silicon monocrystal by alloying into saidv silicon monocrystal a quantity of gold alloy containing from.0.2% to 5% antimony by weight, from 104% lto 101% sulphur `by weight, and containing between 103% to 101% arsenic by weight to form a junction zone between said electrode and said monocrystal, said electrode having an area equal to that of said junction zone.

7. A method for producing an electrode-carrying semiconductor device inV which the semiconductor is composed of silicon, comprising forming at least one electrode of foil thickness on a silicon monocrystal by joining together with said monocrystal a gold alloy of foil thickness containing from 0.2% to 5% antimony by weight and from 104% to 104% sulphur by weight to form a junction zone between said electrode and said monocrystal, said electrode having an area equal to that of said junction zone, whereby faulty alloying spots in said junction zone areminimized.

References Cited in the le of this patent UNITED STATES PATENTS 2,702,360 Geacoletto Feb. 15,' 1955 2,705,768 Kleirnaclc et al. Apr. 5,` 1955 2,865,794 Kroger et a1. Dec. 23, 1958 

1. A METHOD FOR PRODUCING AN ELECTRODE-CARRYING SEMICONDUCTOR DEVICE IN WHICH THE SEMICONDUCTOR IS COMPOSED OF SILICON, COMPRISING FORMING AT LEAST ONE ELECTRON OF FOIL THICKNESS ON A SILICON MONOCRYSTAL BY ALLOYING INTO SAID SILICON MONOCRYSTAL A QUANTITY OF GOLD CONTAINING FROM 0.2% TO 5% ANTIMONY AND A TRACE CONTENT OF SULPHUR TO FORM A JUNCTION ZONE LARGER THAN 1 MM.2 IN AREA, SAID ELECTRODE HAVING AN AREA EQUAL TO THAT OF SAID JUNCTION ZONE, WHEREBY FAULTY ALLOYING SPOTS IN SAID JUNCTION ZONE ARE MINIMIZED. 